Gadolinium-DTPA-Enhanced MR Imaging of Spinal Neoplasms: Preliminary Investigation and Comparison with Unenhanced Spin-Echo and STIR Sequences

Unenhanced T1- and T2-weighted spin-echo, short inversion time inversion recovery (STIR), and gadolinium-DTPA (Gd-DTPA)-enhanced spin-echo and STIR imaging techniques were used in 20 patients as part of a multicenter study to assess the safety and efficacy of Gd-DTPA in spinal imaging. Five patients had normal MR scans. Of those with lesions, both Gd-DTPA-enhanced T1-weighted spin-echo and unenhanced STIR scans improved detection and evaluation of spinal tumors over conventional spin-echo methods, particularly T2-weighted spin echo, by providing higher tissue contrast in shorter imaging times. The Gd-DTPA-enhanced T1-weighted spin-echo scans were most helpful in evaluating intradural tumors, whereas STIR sequences were most effective for extradural tumors and bone metastases. In most cases, Gd-DTPA-enhanced T1-weighted spin-echo scans best delineated tumor margins, and the enhancement was helpful in suggesting a cellular or active nature of the lesions. In some cases, the enhancement resulted in a more homogeneous and thus less abnormal-appearing marrow in vertebrae involved by tumor; therefore, a precontrast T1-weighted spin-echo scan is necessary in all patients who are to be studied with Gd-DTPA.A combined approach that uses T1-weighted spin-echo, Gd-DTPA-enhanced T1-weighted spin-echo, and STIR images currently appears optimal for MR imaging of spinal neoplasms. T2-weighted spin-echo images add information only in occasional cases.     

Gadolinium-DTPA-enhanced MR imaging of spinal neoplasms: preliminary investigation and comparison with unenhanced spin-echo and STIR sequences

Unenhanced T1- and T2-weighted spin-echo, short inversion time inversion recovery (STIR), and gadolinium-DTPA (Gd-DTPA)-enhanced spin-echo and STIR imaging techniques were used in 20 patients as part of a multicenter study to assess the safety and efficacy of Gd-DTPA in spinal imaging. Five patients had normal MR scans. Of those with lesions, both Gd-DTPA-enhanced T1-weighted spin-echo and unenhanced STIR scans improved detection and evaluation of spinal tumors over conventional spin-echo methods, particularly T2-weighted spin echo, by providing higher tissue contrast in shorter imaging times. The Gd-DTPA-enhanced T1-weighted spin-echo scans were most helpful in evaluating intradural tumors, whereas STIR sequences were most effective for extradural tumors and bone metastases. In most cases, Gd-DTPA-enhanced T1-weighted spin-echo scans best delineated tumor margins, and the enhancement was helpful in suggesting a cellular or active nature of the lesions. In some cases, the enhancement resulted in a more homogeneous and thus less abnormal-appearing marrow in vertebrae involved by tumor; therefore, a precontrast T1-weighted spin-echo scan is necessary in all patients who are to be studied with Gd-DTPA. A combined approach that uses T1-weighted spin-echo, Gd-DTPA-enhanced T1-weighted spin-echo, and STIR images currently appears optimal for MR imaging of spinal neoplasms. T2-weighted spin-echo images add information only in occasional cases.     

MR imaging of the muscular component of myocutaneous flaps in the head and neck

BACKGROUND AND PURPOSE: Myocutaneous flaps are commonly used for reconstruction in head and neck surgery. The purpose of this study was to characterize the MR imaging findings of the muscular component of these flaps, with an emphasis on enhancement patterns. Recognition of these imaging findings is important in differentiating postoperative changes from recurrent tumor. METHODS: MR studies were evaluated in 25 patients who had undergone 27 flap reconstructions after resection of a head and neck tumor. Twenty were free flaps and seven were pedicled rotation flaps, and a dominant component of all flaps was muscle. MR images were reviewed for signal intensity, enhancement characteristics, and morphology over a period of 7 to 79 months. RESULTS: On baseline postoperative images, 21 flaps showed moderate or intense enhancement of the muscular graft component relative to nonenhancing native muscle, three flaps showed mild enhancement, and three showed no enhancement. On follow-up images, 18 flaps that initially had intense enhancement showed persistent intense enhancement, and three showed decreasing enhancement. Two flaps with initial mild enhancement were unchanged on follow-up, and one became nonenhancing. None of the initially nonenhancing flaps subsequently enhanced. T1 signal intensity of muscular graft components was always isointense with normal muscle, whereas T2 signal intensity was variable and tended to be stable. Ninety-three percent of our muscular flap components showed striations typical of normal muscle and were best identified on T1-weighted images. No significant imaging differences were found between pedicled and free flaps. CONCLUSION: Most muscular flap components show moderate or intense enhancement on fat-suppressed contrast-enhanced MR images that may persist for many months and be quite striking. Radiologists should be familiar with the typical postoperative appearance of predominantly muscular flaps to avoid misdiagnosis as tumor extension or recurrence.     

MR imaging enhancement patterns as predictors of hemorrhagic transformation in acute ischemic stroke

BACKGROUND AND PURPOSE: Early parenchymal gadolinium enhancement on T1-weighted MR images is predictive of hemorrhagic transformation (HT) in rodent focal ischemia models, but its value in humans is unknown. We sought to investigate gadolinium enhancement in acute ischemic stroke patients to determine their association with subsequent HT. METHODS: We retrospectively examined 22 patients with ischemic stroke who underwent MR imaging within 4.9 hours (+/-1.4) of symptom onset. Patients receiving intravenous tissue plasminogen activator (tPA) (n = 6) were included. Twenty-one patients underwent repeat MR studies at 48 hours, 13 underwent additional MR imaging at 1 week, and one underwent follow-up head CT at 24 hours. Initial images were analyzed for enhancement patterns (vascular, meningeal, parenchymal). Follow-up T2- and T2*-weighted images were evaluated for hemorrhage. RESULTS: In all patients, initial MR images showed vascular enhancement in the vascular territory of the stroke lesion: 19 with vascular enhancement alone and three with vascular and parenchymal enhancement. All three patients with both enhancement patterns had HT: two large and symptomatic, and one asymptomatic (petechial hemorrhage). They received tPA before MR imaging. None of the patients without early parenchymal enhancement developed symptomatic hemorrhage. Six (32%) patients with vascular enhancement alone had petechial hemorrhage at follow-up imaging. In this limited sample, initial mean volumes on diffusion-weighted images, National Institute of Health Stroke Scale scores, and intervals from stroke onset to imaging did not differ between patients with vascular and parenchymal enhancement versus those with vascular enhancement alone. CONCLUSION: Early parenchymal enhancement of stroke lesions may be a good predictor of subsequent symptomatic HT may help identify patients at risk, especially after thrombolytic therapy.     

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.     

Gd-DTPA-enhanced MR imaging of the brain in patients with meningitis: comparison with CT

Plain and Gd-DTPA-enhanced MR images of the brain were obtained in 18 consecutive patients with meningitis (eight with tuberculous, five with bacterial, three with viral, and two with fungal infections); the MR images were compared with CT scans. MR images were obtained on a 2.0-T superconducting unit with both T1- and T2-weighted pulse sequences before injection and with a T1-weighted sequence after injection of Gd-DTPA (0.1 mmol/kg) in all patients. In tuberculous meningitis, MR imaging depicted ischemia/infarct, hemorrhagic infarct of basal ganglia, meningeal enhancement at either basal cistern or convexity surface of brain, and associated small granulomas in a few more patients than CT did. In bacterial meningitis, primary foci of extracranial inflammation (i.e., mastoid, paranasal sinuses) and adjacent intracranial lesions including localized dural inflammation, subdural fluid collection, and/or brain parenchymal lesions were demonstrated much better on MR than on CT. Otherwise, MR images generally matched the CT scan. Although the plain MR images, both T1- and T2-weighted, were the most sensitive in delineating ischemia/infarct, hemorrhage, and edema, they were not as specific as Gd-DTPA-enhanced T1-weighted images and postcontrast CT scans in defining the active inflammatory process of the meninges and focal lesions precisely. We conclude that if Gd-DTPA is used, MR imaging appears to be superior to CT in the evaluation of patients with suspected meningitis. Precontrast MR is needed to delineate ischemia/infarct, edema, and subacute hemorrhage.     

Hepatic metastases: liposomal Gd-DTPA-enhanced MR imaging

Liposomal gadolinium diethylenetriaminepentaacetic acid (DTPA) encapsulated within 70- and 400-nm vesicles was tested as a contrast agent for magnetic resonance (MR) imaging of the liver in rats with hepatic metastases. Liposomal Gd-DTPA caused significant improvement in contrast between liver and tumor (P less than .005) on T1-weighted MR images. Smaller 70-nm liposomal Gd-DTPA vesicles caused greater contrast enhancement, reflecting the larger surface-area-to-volume ratio of the smaller vesicles. Liposomal Gd-DTPA-enhanced images permitted significant improvement in metastasis detection by five blinded radiologists (P less than .005). By comparison, free Gd-DTPA without liposomes caused a statistically significant reduction in contrast between tumor and liver and reduced lesion detection (P less than .01). Liposomal Gd-DTPA also resulted in sustained vascular enhancement for 1 hour after administration. The results suggest that paramagnetic liposomes may become a useful MR imaging contrast agent.     

MR evaluation of frontal sinus osteoplastic flaps with autogenous fat grafts.

PURPOSETo investigate the MR findings in patients who have had osteoplastic frontal sinus flaps placed for inflammatory sinonasal disease.METHODSThe MR images of 13 patients who had improvement of symptoms after osteoplastic frontal sinus flap placement with fat autograft were prospectively evaluated for the presence of high intensity on T2-weighted scans, contrast enhancement, and replacement of frontal sinus fat by lower-signal soft tissue. All studies were performed on a 1.5-T unit using a 5-in round surface coil placed over the nasion. Sagittal T1-weighted, axial and coronal fast spin-echo T2-weighted, and precontrast and postcontrast axial and coronal T1-weighted images were obtained through the operative bed. The T2-weighted and postgadolinium sequences were done with a fat-suppression technique.RESULTSHyperintensity within the frontal sinuses on T2-weighted images and enhancement (peripherally and/or centrally where fat was replaced with soft tissue) were found to some degree in all patients. The degree of replacement of frontal sinus fat with soft tissue ranged from 4% to 85% (mean, 43%). Five patients with persistent symptoms had no distinguishing MR features when compared with asymptomatic patients.CONCLUSIONSAlthough increased T2-weighted intensity, fat replacement, and enhancement are findings compatible with inflammation, these changes may be seen in patients who are asymptomatic after placement of osteoplastic frontal sinus flaps; they may represent the normal granulation process. MR findings after flap placement are nonspecific and have limited utility in distinguishing symptomatic patients with recurrent inflammatory disease from asymptomatic patients whose imaging findings are related to postoperative scar tissue.     

Dynamic contrast-enhanced breath-hold MR imaging of thoracic malignancy using cardiac compensation

The purpose of this paper was to evaluate the use of dynamic gadopentetate dimeglumine-enhanced, breath-hold spoiled gradient-recalled (SPGR) MR imaging with cardiac compensation (CMON) compared to spin-echo MR imaging in patients with thoracic malignancy. We retrospectively reviewed MR images from 29 patients with thoracic tumors. MR imaging included axial electrocardiogram (ECG)-gated T1-weighted, fast spin echo (FSE) T2-weighted, and contrast-enhanced breath-hold fast multiplanar SPGR imaging with CMON, which selects the phase-encoding gradient based on the phase within the cardiac cycle. Images were reviewed for lung masses, mediastinal or hilar tumor, disease of the pleura, chest wall, and bones, and vascular compression or occlusion. Contrast-enhanced fast multiplanar SPGR imaging with CMON produces images of the chest that are free of respiratory artifact and have diminished vascular pulsation artifact. ECG-gated T1-weighted images were preferred for depicting mediastinal and hilar tumor. The gadopentetate dimeglumine-enhanced fast multiplanar SPGR images were useful for depicting chest wall tumor, vascular compression or thrombosis, osseous metastases, and in distinguishing a central tumor mass from peripheral lung consolidation. Pleural tumor was depicted best on the FSE T2-weighted images and the contrast-enhanced SPGR images. As an adjunct to spin echo T1-weighted and T2-weighted imaging, contrast-enhanced fast multiplanar SPGR imaging with CMON is useful in the evaluation of thoracic malignancy.     

Relationship between vascular enhancement, cerebral hemodynamics, and MR angiography in cases of acute stroke

BACKGROUND AND PURPOSE: The use of MR angiography and contrast-enhanced T1-weighted MR imaging in cases of acute cerebral ischemia may be helpful in the evaluation of middle cerebral artery (MCA) occlusion and leptomeningeal collaterals, respectively. The aim of our work was to investigate the relationship between MCA occlusion, T1-weighted vascular contrast enhancement, hemodynamic alterations, and tissue damage in cases of acute ischemic stroke. METHODS: We studied the MCA territory in 15 patients with acute ischemic stroke within 8 hr of symptom onset. The first MR imaging study (<8 hr after onset) comprised diffusion-weighted imaging, MR angiography, perfusion-weighted imaging, and contrast-enhanced T1-weighted MR imaging sequences. Follow-up MR imaging, performed 1 week later, consisted of MR angiography and T2-weighted fluid-attenuated inversion recovery MR imaging. RESULTS: Early MR angiography showed MCA stem occlusion in nine of 15 patients. Patients with MCA occlusion had significantly larger areas of abnormality on early diffusion-weighted images, significantly larger areas of altered hemodynamics, larger final lesion volumes, and poorer clinical outcome. Among the nine patients with MCA stem occlusion, vascular enhancement was marked in seven and absent in two who had complete MCA infarcts and poor clinical outcome. Among patients with MCA patency, vascular enhancement was marked in only one, mild in four, and absent in one. Patients with marked vascular enhancement had significantly larger regions of altered hemodynamics and significantly higher asymmetries in both regional cerebral blood volume and mean transit time because of increased values in the affected hemisphere. CONCLUSION: Among patients with stroke with MCA occlusion, marked vascular enhancement and increased blood volume indicate efficient leptomeningeal collaterals and compensatory hemodynamic mechanisms.     

Gd-DOTA-enhanced MR imaging and color Doppler US of renal allograft necrosis.

In 21 recipients of renal transplants suspected of allograft necrosis, the authors correlated the results of imaging to pathologic and histologic data in order to describe the magnetic resonance (MR) imaging and color Doppler ultrasonographic (US) characteristics of infarction. All patients underwent MR imaging performed with and without gadolinium tetraazacyclododecanetetraacetic acid (DOTA) and color Doppler US. Nonenhanced T1-weighted images showed no obvious changes, whereas nonenhanced T2-weighted images demonstrated a slight increase in signal intensity in areas of ischemic necrosis and low or heterogeneous signal intensity in areas of hemorrhagic necrosis. Gd-DOTA-enhanced MR images showed no contrast material uptake in infarcted areas. Color Doppler US characteristics of infarction included absence of Doppler signal and alteration of the cortical echogenic structure, particularly in cases of ischemic necrosis. Color Doppler US allows measurement of vascular resistance and assessment of intrarenal vasculature and the renal pedicle. Gd-DOTA-enhanced MR imaging is useful in confirming the diagnosis of infarction and provides an accurate evaluation of the extent of the infarct.     

MR imaging of compartment syndrome of the lower leg: a case control study

The aim of this study was to evaluate the use of MR imaging for diagnosis and therapy management of compartment syndromes. In total, 15 patients (5 with an imminent compartment syndrome and 10 with manifest compartment syndrome) underwent MR imaging with a variety of pulse sequences including fat suppression, magnetization transfer imaging, and intravenous gadopentetate dimeglumine (Gd-DTPA) administration. Early and late follow-up MR images were obtained. Manifest compartment syndromes showed swollen compartments with loss of normal muscle architecture on T1-weighted spin-echo images. T2-weighted spin-echo and magnetization transfer imaging showed bright areas, which enhanced after Gd-DTPA. Early follow-up showed changes in enhancement patterns; late follow-up showed fibrosis and cystic and fatty degenerations of the affected compartments. MR imaging can help make the diagnosis of a manifest compartment syndrome in clinically ambiguous cases. It points out the affected compartments and allows the surgeon to selectively split the fascial spaces.     

Hyperacute ischemic stroke: middle cerebral artery susceptibility sign at echo-planar gradient-echo MR imaging

PURPOSE: To evaluate the accuracy of echo-planar T2*-weighted magnetic resonance (MR) sequences in detection of acute middle cerebral artery (MCA) or internal carotid artery (ICA) thrombotic occlusion. MATERIALS AND METHODS: Forty-two consecutive patients with stroke involving the MCA territory underwent MR imaging within 6 hours after clinical onset. MR examination included echo-planar T2*-weighted, diffusion-weighted (DW), and perfusion-weighted (PW) imaging and MR angiography. Presence or absence of the susceptibility sign on echo-planar T2*-weighted images, which is indicative of acute thrombotic occlusion involving MCA or ICA, was assessed in consensus by two observers blinded to clinical information and other MR imaging data. Differences in lesion volume on DW and PW images between patients with and those without the susceptibility sign were evaluated with the Mann-Whitney test. P <.05 was considered to indicate a significant difference. RESULTS: Thirty patients (71%) had a positive susceptibility sign that correlated with MCA or ICA occlusion at MR angiography in all cases (sensitivity, 83%; specificity, 100%). Mean lesion volume on PW images was higher in patients with a positive susceptibility sign (P =.01), but no significant differences were found in mean lesion volume on DW images. Cases in which the susceptibility sign was identified proximal to MCA divisional bifurcation (27 patients) showed a mean perfusion deficit of 83.9% of the total MCA territory (range, 50%-100%). CONCLUSION: Presence of the susceptibility sign proximal to MCA bifurcation provides fast and accurate detection of acute proximal MCA or ICA thrombotic occlusion.     

Gadolinium-DOTA enhanced MR imaging of adnexal tumors

We conducted a retrospective study to assess the potential of contrast enhanced magnetic resonance (MR) imaging in evaluating adnexal tumors. Sixty patients with a total of 77 pelvic lesions underwent MR imaging at 1.5 T and transabdominal ultrasound (US). Precontrast T1- and T2-weighted and Gd-DOTA enhanced T1-weighted MR images were obtained. Diagnoses were proved by surgery in 57 patients. Of the 77 lesions, 54 masses were of ovarian origin, including 12 malignant disorders. Ultrasound demonstrated the lesions in 92%, whereas the sensitivity of unenhanced T2-weighted and postcontrast MR images was 98 and 96%, respectively. Compared to the T2-weighted images, postcontrast MR imaging showed superior overall tumor delineation, assessment of intratumoral architecture, and definition of tumor origin. Contrast enhancement of tumors did not differ significantly between normal ovary and benign and malignant lesions. All modalities were unable to predict malignancy of complex lesions. Based on our study, US remains the screening modality of choice in the evaluation of adnexal tumors. Contrast enhanced MR imaging may be valuable for assessing complex lesions or when the origin of the mass cannot be determined by US. Using contrast enhanced T1-weighted images instead of T2-weighted images may lead to a significant reduction in acquisition time.     

Bithalamic hyperintensity on T2-weighted MR: vascular causes and evaluation with MR angiography.

PURPOSETo determine whether MR angiography can be used to differentiate between the two vascular causes of bithalamic hyperintensity on T2-weighted MR images: "top of the basilar" artery occlusion and deep cerebral vein thrombosis.METHODSA retrospective review identified six patients with bithalamic T2 hyperintensity of vascular causes. MR angiography was performed in four patients, MR angiography and conventional angiography in one patient, and conventional angiography in one patient. Data pertaining to clinical presentation and hospital course were collected. MR angiographic techniques were multislab overlapping three-dimensional time-of-flight, 2-D time-of-flight, and 2-D phase-contrast.RESULTSThree cases of top of the basilar artery occlusion and three cases of deep cerebral vein thrombosis were recognized. In all cases, T2 hyperintensity in a vascular distribution suggested cerebral occlusive disease. Infarction involving the thalami and basal ganglia was present in two cases of deep cerebral vein thrombosis. Infarction of the thalami, mesodiencephalic region, and cerebellar hemispheres was present in two cases of basilar artery occlusion. Bithalamic infarction alone was seen in one case of deep cerebral vein thrombosis and one case of basilar artery occlusion. In the five cases in which MR angiography was used, this technique accurately distinguished the vessels involved (arterial or venous).CONCLUSIONMR angiography is a useful adjunct to MR imaging in the evaluation of bithalamic T2 hyperintensity. It does help distinguish between the two vascular causes: top of basilar artery occlusion and deep cerebral vein thrombosis.     

Assessment of osteosarcoma response to preoperative chemotherapy using dynamic FLASH gadolinium-DTPA-enhanced magnetic resonance mapping.

RATIONALE AND OBJECTIVES. To improve the accuracy of magnetic resonance imaging (MRI) in evaluating the response of osteosarcomas to preoperative chemotherapy, the authors developed a technique of mapping tumor necrosis and viability by quantitating slope values of gadolinium-DTPA (Gd-DTPA) uptake on dynamic fast low-angle shot (FLASH) images. METHODS. Dynamic contrast-enhanced FLASH imaging of a single representative plane was performed on six osteosarcomas. Tumors were mapped by dividing resultant images into contiguous regions of interest and deriving slopes representing percentage increase in signal intensity (SI) per minute over the baseline for each region. The results were compared with estimations of viable tumor volume on subtracted Gd-DTPA-enhanced T1-weighted images and histologic maps of necrotic and viable tumor. RESULTS. Dynamic FLASH estimations of percent tumor necrosis using a critical slope value of 45% per minute correctly predicted histologic response to chemotherapy in all six patients. Comparison of dynamic FLASH and histologic maps showed a high degree of correlation. Static enhanced T1-weighted images overestimated the amount of residual viable tumor. CONCLUSIONS. Dynamic FLASH Gd-DTPA-enhanced mapping is a potentially useful noninvasive method of quantitating tumor response to chemotherapy.     

Musculoskeletal neoplasms after intraarterial chemotherapy: correlation of MR images with pathologic specimens

The most accurate prognostic indicator in patients with musculoskeletal sarcomas is the percentage of tumor necrosis after intraarterial chemotherapy. Magnetic resonance (MR) imaging was evaluated to determine its ability to indicate the percentage of necrosis in musculoskeletal neoplasms after treatment. Fourteen patients with musculoskeletal neoplasms underwent treatment protocols including intraarterial chemotherapy (n = 14), radiation therapy (n = 6), and systemic chemotherapy (n = 14). All patients underwent MR imaging before and after treatment, and all underwent either limb salvage surgery (n = 8) or amputation (n = 6) within 1 week of the last MR examination. Standard unehanced spin-echo T1-, spin-density-, and T2-weighted MR sequences were used. The MR images were compared with the pathologic specimens. On T2-weighted images, the signal intensities of viable tumor, tumor necrosis, edema, hemorrhage, and necrosis overlapped. With the unenhanced spin-echo technique, MR imaging cannot be used to predict the percentage of tumor necrosis in musculoskeletal neoplasms after intraarterial chemotherapy.     

MR imaging of reperfused myocardial infarction: comparison of necrosis-specific and intravascular contrast agents in a cat model

PURPOSE: To compare T2-weighted and Gadomer-17- and bis-gadolinium mesoporphyrins-enhanced magnetic resonance (MR) images for distinguishing reversibly from irreversibly damaged myocardium in a cat model of reperfused myocardial infarction. MATERIALS AND METHODS: Twelve cats underwent 90 minutes of occlusion and 90 minutes of reperfusion of the left anterior descending coronary artery. After baseline T1- and T2-weighted MR images were obtained, Gadomer-17-enhanced and bis-gadolinium mesoporphyrins-enhanced T1-weighted images were sequentially obtained for 6 hours and 2 hours, respectively. After MR imaging, all cats were sacrificed for 2,3,5-triphenyltetrazolium chloride (TTC) histochemical tissue staining. Areas of abnormal signal intensity on T2-weighted and Gadomer-17-enhanced and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images were compared with the areas of infarction seen at TTC histochemical staining by using repeated-measures two-way analysis of variance, linear regression analysis, and Bland-Altman analysis. RESULTS: Mean areas of abnormally high signal intensity on T2-weighted and Gadomer-17-enhanced T1-weighted MR images (43.9% of the left ventricular surface area +/- 11.9 [SD] and 37.7% +/- 10.1, respectively) were significantly larger than the mean area of myocardial infarction at TTC staining (25.7% +/- 12.5) (P <.001). However, there was excellent correlation between the size of an enhancing area on bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images and that of myocardial infarction at TTC staining (r = 0.916, P <.001). CONCLUSION: bis-Gadolinium mesoporphyrins-enhanced T1-weighted MR images accurately reflect the area of infarction, whereas the size of infarction is overestimated on T2-weighted and Gadomer-17-enhanced T1-weighted MR images, which seem to depict the periinfarct area as well as the infarct area.     

Pelvic reconstruction with omental and VRAM flaps: anatomy, surgical technique, normal postoperative findings, and complications

Soft-tissue reconstruction of the pelvis with vascularized tissue flaps has become an increasingly common procedure. The types of flaps and the indications for their use vary, but all flap procedures are performed with the goal of transferring tissue from a donor site to a recipient site to restore form and function, obliterate dead space, and create an environment favorable to wound healing. Oncologic surgeries, including total pelvic exenteration and abdominoperineal resection, are the leading indications for pelvic reconstruction. The pedicle flaps most commonly used for pelvic reconstruction following these oncologic interventions are the vertical rectus abdominis myocutaneous flap (VRAM) and the omental pedicle flap. Familiarity with the surgical techniques used for pelvic reconstruction with these flaps is crucial for the accurate interpretation of cross-sectional imaging studies, allowing the radiologist to distinguish between normal postoperative findings and complications or recurrent disease.     

Gd-DTPA-enhanced MR imaging in pediatric patients after brain tumor resection

A prospective study was conducted in 15 pediatric patients who had undergone resection of intracranial tumors. The object of the study was to determine the safety and efficacy of magnetic resonance (MR) imaging performed after the administration of gadolinium diethylenetriamine-pentaacetic acid (Gd-DTPA) in evaluating residual or recurrent tumor. Precontrast T1-weighted, intermediate, and T2-weighted images were obtained at a field strength of 1.5 T. Gd-DTPA was then injected intravenously in a dose of 0.1 mmol per kilogram of body weight. T1-weighted images were obtained within 5 minutes after the injection, intermediate and T2-weighted images were obtained 10 minutes after the injection, and T1-weighted images were obtained approximately 20 minutes after the injection. None of the patients experienced allergic reactions or other side effects. Physical examination findings and laboratory values were unchanged after the Gd-DTPA-enhanced examination. In six patients, contrast-enhanced images depicted tumor not suspected on nonenhanced images. In four other patients, enhanced images provided better definition of the tumor core. The images of one patient with a brain stem tumor showed no evidence of enhancement. Pre- and postcontrast images of three previously treated patients showed no evidence of tumor. Gd-DTPA appears to be a safe and effective contrast agent for MR imaging and provides a more accurate method of imaging in the follow-up of brain tumors in pediatric patients.